Precipitation that falls onto a site and hits impervious surfaces, such as a roof, and then runs off is considered rainwater. Rainwater has been collected for as long as humans have been around, and there are several innovative and intelligent systems that use rainwater collection as a source for freshwater. Rainwater is naturally produced and is the cleanest of the three types present in a net-zero water system. Because of this, it requires light filtration followed by UV sterilization to be used for potable purposes.
The amount of rainwater available to a property varies heavily on the climate of where the property is and the time of the year. In our region of Philadelphia, rainwater falls at a pretty even rate, but still fluctuates depending on the month. Here’s a list of average rainfall for the Philadelphia region:
Treated rainwater will be primarily used for potable purposes, mainly the kitchen sink and dishwasher, as well as showers and bathroom sinks throughout a household. If there is an overabundance of rainfall during a certain period of time, or a lack of greywater being produced and treated, “raw,” or lightly treated rainwater can be used for purposes such as irrigation, toilet flushes, and washing machines.
[...] order to achieve water independence, a building must capture all precipitation, manage all storm water runoff, and re-use all household wastewater. ”Wastewater” can [...]
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